Raytheon Company

Gerard J Shaw

Jok Y Go

Bruce G Armstrong

Jerry W Drake

Rajni Kant

Deepak Mehrotra

Jay H Chun

A memory cell comprising a memory region of amorphous silicon, such memory region having a first state of substantial electrical nonconductivity programmable to a second state of substantial electrical conductivity in response to an electrical programming signal applied thereto. The memory region is disposed over a metal Schottky contact, such as platinum-silicide (PtSi), formed in a support body. A first barrier layer comprising a refractory metal such as titanium-tungsten (TiW) is disposed between the memory region and Schottky contact. A first input terminal comprising a metal strip conductor, such as aluminum, is disposed over the memory region, with a second refractory metal barrier layer being disposed between the memory region and metal strip conductor. A second input terminal is disposed within the support body. With such arrangement, the material of the Schottky contact (PtSi) is substantially prevented from migrating or diffusing into the silicon memory region upon application of the electrical programming signal between the first and second input terminals, thereby preserving the structure of the metal contact and maintaining a low reverse bias leakage current for a Schottky diode comprising such metal contact. Also, the level of the programming signal may be increased, providing more complete programming of the memory region to the second, electrically conductive state.

Programmable memory cell structure including a refractory metal barrier

A semiconductor structure is provided comprising a bulk substrate of semiconductor material having a first-type doping conductivity in a first dopant concentration. A first layer of semiconductor material is epitaxially formed on the substrate, such first layer having the first-type doping conductivity in a second dopant concentration lower than the first concentration. A second layer of semiconductor material is epitaxially formed on the first layer, the second layer having a second-type doping conductivity opposite to the first-type doping conductvity and thereby forming a P-N junction with the first layer. A plurality of regions, comprising semiconductor material having the first-type doping conductivity and extending through the second layer and a predetermined distance into the first layer, are further included for providing electrical isolation between active devices formed in different regions of the second layer. The thickness of the first layer is selected to be greater than the diffusion lengths of electron-hole pairs emitted by the bulk substrate in response to incident radiation and smaller than the thickness of the bulk substrate. With such arrangement, electron-hole pairs emitted by the substrate are substantially prevented from reaching such P-N junction, and few electron-hole pairs are emitted by the first layer, due to the small thickness thereof. Thus, electron-hole current at such P-N junction is reduced, thereby decreasing the effects of incident radiation on active devices formed in the semiconductor structure.

Semiconductor device

A semiconductor device fabrication process is provided wherein a first window is formed in a first silicon dioxide layer which is disposed over the surface of a silicon layer to expose a first portion of the silicon layer. A doped region is formed in the first portion of a silicon layer exposed by the first window. A second layer of silicon dioxide is deposited over the surface of the first, previously formed, silicon dioxide layer and over the first portion of the silicon layer exposed by the first window. A second window is formed through the first and second silicon dioxide layers to expose a second, different portion of the surface of the silicon layer. A layer of silicon nitride is disposed over the second layer of silicon dioxide and through the second formed window onto the portion of the silicon layer exposed by such second formed window. The surface of the structure is then masked with windows being formed in such mask over the first and second previously exposed portions of the silicon layer. An etchant is brought into contact with portions of the silicon nitride layer exposed by the windows formed in the mask to selectively remove the portions of the silicon nitride layer exposed by such windows and to thereby expose the portion of the second silicon dioxide layer disposed over the first exposed portion of the silicon layer and the second exposed portion of the silicon layer. A Schottky contact metal is deposited over the surface of the structure and onto the second exposed portion of the silicon layer to form a Schottky contact region. The portion of the second silicon dioxide layer disposed over the first exposed portion of the silicon layer is then selectively removed with a chemical etchant to expose a portion of the previously formed doped region.

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San Jose, CA, United States of America

Gerard J Shaw